Field of the Invention
The present invention concerns wireless communications, and more specifically, to methods of scheduling a service period for transmission of data in a Wireless Local Area Network (WLAN) system and transmitting and receiving data based on the service period and apparatuses supporting the same.
Related Art
With the growth of information communication technology, various wireless communication technologies have been recently developed. Among others, Wireless Local Area Network (WLAN) is a technology that allows for wireless access to the Internet at home or business or in a specific service area using a handheld terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), etc.
IEEE 802.11n is a technology standard that has been recently established in order to overcome the limit to communication speed that has been recognized as a weakness of WLAN. IEEE 802.11n aims to increase network speed and reliability and expand coverage of a wireless network. More specifically, the IEEE 802.11n system adopts MIMO (Multiple Inputs and Multiple Outputs) technology that uses multiple antennas at both a transmission unit and a reception unit thereof so as to optimize data speed and to minimize transmission errors while supporting a high throughput (HT) of data processing speed up to 540 Mbps.
In the WLAN system, a station (STA) supports a power save mode. The station may prevent unnecessary power consumption by entering into a doze state. In case there is traffic associated with data that intends to be sent to a STA that is operating in a doze state, an access point (AP) may notify this to the STA. The STA recognizes existence of traffic associated with data intended to be sent thereto and may request that the AP be sending it to the STA. The AP may transmit a frame in response to the STA's request.
Meanwhile, if an AP can transmit only one frame in response to a request of an STA that has entered into the awake state, it may be insufficient in light of data processing. Further, in order to receive frames, the STA shifts between awake state and doze state more frequently, thus deteriorating efficiency in terms of power saving operation. Accordingly, a need exists for a method for scheduling a service period that may support an efficient operation of the STA.